Previously, we have demonstrated waterlogging and increased sodium content and decreased distensibility of veins in the various models of experimental hypertension and in human hypertension. The findings suggested that circulating humoral factors may participate in the pathogenesis of abnormal vascular wall composition and function in hypertension. Evidence for the role of circulating humoral substances in the pathogenesis of abnormal vascular wall composition in hypertension was provided from experiments in which rabbit aorta explants were cultured in tissue culture medium supplemented with serum obtained from dogs during a pre-hypertension control period and after the induction of one-kidney perinephritic hypertension (1-KPHT). After 3 weeks of culture, the water and sodium content of explants cultured in hypertension serum was increased. In the proposed study, the role of tissue glycosaminoglycans and of sodium binding in the pathogenesis of these changes will be investigated. The effect of ouabain on the composition of rabbit aorta explants in tissue culture will be studied as a possible model for the effects of 1-KPHT serum on vascular wall composition.